Paper proposal: Pion femtoscopy at sqrt(s) = 3 GeV
Title: Pion femtoscopy at √sNN = 3 GeV in STAR
PA: Anna Kraeva, Youquan Qi, Vinh Luong, Grigory Nigmatkulov and Xiaofeng Luo
Contact information: annakraeva555@gmail.com, qyq@mails.ccnu.edu.cn, lbavinh@gmail.com, nigmatkulov@gmail.com, xfluo.star@hotmail.com
Target journal: Physical Review C
Talks in PWG:
1) https://drupal.star.bnl.gov/STAR/system/files/Corr_function_3gev_Kraeva.pdf
2) https://drupal.star.bnl.gov/STAR/system/files/Corr_function_3gev_Kraeva_meeting2.pdf
3) https://drupal.star.bnl.gov/STAR/system/files/Corr_fctn_meeting3_0.pdf
4) https://drupal.star.bnl.gov/STAR/system/files/Collab%20meeting%201%20dec%20Kraeva.pdf
5) https://drupal.star.bnl.gov/STAR/system/files/Meeting_1_June.pdf
6) https://drupal.star.bnl.gov/STAR/system/files/Meeting_8_June.pdf
Systematical uncertainty estimation:
1) https://drupal.star.bnl.gov/STAR/system/files/Pion_CF_workshop20230629.pdf
2) https://drupal.star.bnl.gov/STAR/system/files/2023.07.27_PWGCF_pion_femtoscopy_in_3p2gev_3p9gev_FXT.pdf
3) https://drupal.star.bnl.gov/STAR/system/files/Preliminary_27_July.pdf
PWG preview (6 July and 12 October 2023):
1) https://drupal.star.bnl.gov/STAR/system/files/Paper_Proposal_plots_6_July.pdf
2) https://drupal.star.bnl.gov/STAR/system/files/Paper_Proposal_plots_v2.pdf
Preliminary figures:
1) https://drupal.star.bnl.gov/STAR/blog/annakraeva/Preliminary-pion-femtoscopy-3-GeV
2) https://drupal.star.bnl.gov/STAR/blog/lbavinh/Preliminary-figures-pion-femtoscopy-3-3p2-3p5-3p9-GeV
Analysis note: link
Abstract:
Femtoscopic correlations of π+π+ and π-π- pairs are studied in fixed-target Au+Au collisions at sqrt(sNN) = 3 GeV by the STAR experiment at RHIC. The three-dimensional analysis is performed as a function collision centrality, pair transverse momentum kT and rapidity ypair. Extracted femtoscopic radii (Rout, Rside, Rlong) decrease with increasing transverse momentum, while correlation strength parameter (λ) decreases with kT. Rside decreases with increasing rapidity, R2out-long depends on the pair rapidity due to symmetry in longitudinal direction. UrQMD calculations qualitatively describe results.
Motivation:
Study spatial and temporal properties of the pion emitting source at low sqrt(sNN). Provide high-statistics femtoscopic radii measurements to measure system evolution as a function of collision energy. Check the difference between π+ and π— emission process at 3 GeV. Detailed measurement of femtoscopic radii dependence as a function of pair transverse momentum, rapidity and collision centrality. Provide unique set of measurements for model constraints.
Figure 1: (top panel) The particle identification using dE/dx in the TPC. (bottom panel) The particle identification using m2 from TOF.
Figure 2: Analysis acceptance in transverse momentum versus pion rapidity in the center-of- mass frame in Au+Au collisions at √sNN = 3.0 GeV
Figure 3: (Top panels) One-dimensional projections of three-dimensional correlation functions onto the “out”, “side” and “long” axes for positive (red markers) and negative (blue markers) pion pairs with 0.15 < kT < 0.25 GeV/c for 0–10% Au+Au central collisions at sqrt(sNN) = 3 GeV. For each projection q_i shown, the other components of relative momentum are integrated over ±50 MeV/c. (Bottom panels) Ratio of one-dimensional projections of correlation functions for positive and negative pion pairs. The ratio of projections is within 5%.
Figure 4: One-dimensional projections of three-dimensional correlation functions onto the “out”, “side” and “long” axes for negative (top panels) and positive (bottom panels) pions with kT: (0.15 - 0.25), (0.25 - 0.35), (0.35 - 0.45), (0.45 - 0.55), (0.55 - 0.65) GeV/c for 0–10% central Au+Au collisions at sqrt(sNN) = 3 GeV. For each projection q_i shown, the other components of relative momentum are integrated over ±50 MeV/c.
Figure 5: Femtoscopic parameters Rout(a), Rside(b), Rlong(c), λ (d), R2out-long(e) dependence on pair transverse momentum for 0–10%, 10–30%, 30–50% centrality bins in Au+Au collisions at sqrt(sNN) = 3 GeV.
Figure 6: Acceptance of positively (left panel) and negatively (right panel) charged pion pairs for Au+Au collisions at sqrt(sNN) = 3 GeV. Dashed lines denote the selected rapidity windows for the rapidity-differential analysis.
Figure 7: Femtoscopic parameters Rout(a), Rside(b), Rlong(c), λ (d), R2out-long(e) dependence on pair rapidity for 0–10%, 10–30%, 30–50% centrality bins in Au+Au collisions at sqrt(sNN) = 3 GeV.
Figure 8: Extracted pion source Rout, Rside, Rlong radii (top panels), correlation strength λ, and Rout/Rside, R^2_out–R^2_side (bottom panels) as a function of colliding energy sqrt(sNN). Red markers denote results from this analysis.
Conclusions:
Femtoscopic measurements of charged pions produced in Au+Au collisions at √sNN = 3 GeV are presented. Correlation functions of positive and negative pions differ slightly for small kT, which may be due to residual electric charge Rout, Rside, Rlong decrease with pair transverse momentum due to transverse flow. The dependence of the λ, Rout, Rside, Rlong, R2out-long on the pair rapidity and centrality (0-10%, 10-30%, 30-50%) was presented:
1) Rapidity dependence of R2out-long is due to symmetry in longitudinal direction
2) Decrease of Rside with increasing rapidity shows a hint of the boost-invariance breaking
UrQMD calculations: 1) Qualitatively reproduce experimental data
2) Demonstrate overestimation of emission duration and underestimation of geometrical size
Additional materials:
1. Comments from the PWG preview
- annakraeva's blog
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